1. Field of Invention
The present invention relates generally to an air intake system and more particularly to a hydrocarbon trap for adsorbing hydrocarbons in the air intake system.
2. Related Technology
Due to laws requiring the reduction of the levels of hydrocarbons that vehicles may emit into the atmosphere, it is necessary for automotive designers to include systems in vehicles to control emissions. Hydrocarbons are released in a vehicle's exhaust, as well as from the engine, even when it is not operating. Hydrocarbons remaining from engine reactions can leak out of the engine through the engine's air intake system. It is therefore beneficial to reduce the level of hydrocarbons released from both the exhaust and the engine via the air intake system.
One device for retaining hydrocarbons from the air released through the engine's intake is a filter-like device having a hydrocarbon trapping element. Typically, the hydrocarbon trapping device is formed of monolith carbon that is disposed in the air induction system of a motor vehicle. More specifically, the hydrocarbon trapping device is typically located in an air intake conduit that provides air to the engine for combustion. Therefore, when the engine is operating and air is flowing through the conduit towards the engine, the hydrocarbon trapping device is considered to be upstream from the engine.
The hydrocarbon trapping device operates by adsorbing hydrocarbons from the low velocity flow that occurs while the engine is not in operation. When the engine is not in operation air leaks out of the air intake system and into the atmosphere. During engine operation, high velocity flow through the air intake system purges the device of trapped hydrocarbons and flushes the hydrocarbons into the vehicle engine.
One problem arising with the hydrocarbon trapping device, however, is that the adsorbing element can become saturated with hydrocarbons; substantially reducing or ceasing adsorption of hydrocarbons. Therefore, in order to effectively trap hydrocarbons and to substantially prevent saturation of the device, it is advantageous to increase the adsorption capacity of the hydrocarbon trapping device.
Another problem associated with hydrocarbon trapping devices is that the devices may act as an obstruction to the air flowing to the engine, thus causing a pressure drop in the airflow to the engine. Therefore, in order to substantially reduce or prevent a drop in air pressure across the hydrocarbon trapping device, it is advantageous to increase the amount of air that can flow through the device.
Yet another problem associated with hydrocarbon trapping devices is that the devices may not have the strength to sustain structural integrity during operation. This problem is especially evident in cases where the device includes a large cross-sectional area—such as a cross-sectional area designed to permit a large volume of air to flow therethrough.
Therefore, it is highly desirable to have a hydrocarbon trapping device that is able to adsorb a relatively large amount of hydrocarbons without becoming saturated, while substantially preventing large airflow pressure drops and maintaining a sufficient structural strength throughout the life of the device.